Short answer. Yes. Rule 109, Section 1(b) of the Rules of Court allows an interested person to appeal from an order or judgment that determines who are the lawful heirs of a deceased person, or the distributive share of the estate to which such person is entitled, without waiting for the entire estate proceeding to be finished.
What the law says
An interested person may appeal in special proceedings from an order or judgment rendered by a Court of First Instance or a Juvenile and Domestic Relations Court, where such order or judgment:
Rule 109, Section 1 — Orders or judgments from which appeals may be taken. Read the full provision →
What the law says
Determines who are the lawful heirs of a deceased person, or the distributive share of the estate to which such person is entitled
Rule 109, Section 1 — Orders or judgments from which appeals may be taken. Read the full provision →
What the law says
Constitutes, in proceedings relating to the settlement of the estate of a deceased person, or the administration of a trustee or guardian, a final determination in the lower court of the rights of the party appealing, except that no appeal shall be allowed from the appointment of a special administrator
Rule 109, Section 1 — Orders or judgments from which appeals may be taken. Read the full provision →
The heir determination is on the list of appealable orders
Rule 109, Section 1 sets out a list of specific orders or judgments in special proceedings that an interested person may appeal, and it opens with: an interested person may appeal in special proceedings from an order or judgment rendered by a Court of First Instance or a Juvenile and Domestic Relations Court, where such order or judgment: Among the items on that list is exactly the ruling you are asking about: determines who are the lawful heirs of a deceased person, or the distributive share of the estate to which such person is entitled.
Why it does not have to wait for the whole case to close
Special proceedings like estate settlement are handled differently from an ordinary civil case, where you typically wait for one final judgment before appealing anything. Section 1 instead names several specific kinds of rulings, the heir determination among them, as independently appealable. The section explains the underlying idea for rulings of this type: they constitute, in proceedings relating to the settlement of the estate of a deceased person, or the administration of a trustee or guardian, a final determination in the lower court of the rights of the party appealing.
The estate proceeding itself can remain open
Because the heir determination is treated as final as to that particular issue, an appeal from it does not require the entire estate settlement to be wrapped up first. The court can go on handling the rest of the estate, distribution, accounting, and other matters, while the ruling on who qualifies as a lawful heir is separately taken up on appeal, since Section 1 lists it as its own appealable determination rather than folding it into the eventual closing order.
What this means for your probate case
If the probate court has issued a ruling on who counts as a lawful heir, that ruling falls within Section 1's list and is appealable now, without waiting for the estate case to be closed entirely. Other aspects of the proceeding, such as settling the executor's or administrator's accounts, are covered by their own separate items in the same section, but the heir determination does not depend on those other matters being finished first.